1. Field of the Invention
The present invention relates generally to the fabrication of objects using fiber composite materials, and more specifically a technique for forming an object, such as a portion of a rotor blade for an aircraft, having a cross-sectional shape which varies along its length.
2. Description of Prior Art
Because of considerations such as weight and strength, fiber composite materials are seeing increasing use in high-tech structures, such as aircraft parts. They are seeing increasing use in aircraft parts such as air foils, rotor blades, and similar parts.
The design of some parts is fairly complex, and results in structures which are not easily fabricated. An example of such a structure are blade components for a helicopter rotor or aircraft propeller. Such blades often have a primary load bearing structure, typically fabricated along the leading edge of the blade. Such a structure is referred to herein as a spar. For some aircraft types, in particular helicopter rotors and rotors for tilt-rotor aircraft, the shape of the spar is relatively complex.
For example, a spar for a tilt-rotor aircraft rotor blade may be on the order of fifteen to thirty feet in length. Along the length of the spar, the cross-sectional area changes, as well as the shape of each cross-section. In addition, the spar includes a twist for aerodynamic purposes.
Numerous techniques are available for fabricating spars using fiber composite materials, but prior art techniques are not always suitable to state-of-the-art objects. For example, one technique for fabricating a spar for a tilt-rotor aircraft blade involves formation of the object in two pieces. A top half and a bottom half are each separately formed on a shaped mold, and then coupled together on another shaped mold. Attaching the two pieces together typically involves deformation of the two originally molded halves. Such techniques tend to be expensive both in terms of assembly time and labor, and in tooling to make the product.
To enhance strength and stiffness of the product, it is desirable that as many fibers as possible be laid full length along the spar. Because of the complex nature of the spar shape, this can be difficult using prior art techniques.
It would be desirable to provide a technique, and the resulting product, for manufacturing complex shapes such as rotor spars for tilt-rotor aircraft rotor blades. It would be desirable for the technique to be relatively inexpensive in both manufacturing and tooling costs, and to provide an accurate reproduction of an intended complex shape.